Novel combination of 2-methoxyestradiol and cyclophosphamide enhances the antineoplastic and pro-apoptotic effects on S-180 ascitic tumour cells.

Sarcoma 180 (S-180) tumour cell line is a stable murine tumour cell line with 98-99% stumour takes capacity in Swiss albino mouse - Mus musculus. 2 Methoxyestradiol (2ME) - a promising anti-neoplastic and anti-angiogenic agent, showed toxicity to host body in higher concentration. Cyclophosphamide (CP), the anti-neoplastic agent has long been used as a chemotherapeutic drug for treatment of different cancers. Our studies have shown that the combination effect of 2ME and CP on S-180 tumour cell line is anti-proliferative and less toxic. The treatment with lower concentrations of 2ME and CP (6.5 mg 2ME/kg body weight + 75 mg CP/kg body weight) antagonistically increased the life span of tumour bearing mice and synergistically inhibited the viable cell population. 2ME or CP treatment individually induces G2/M arrest. The combination treatment of 2ME + CP (6.5 mg 2ME/kg body weight + 75 mg CP/kg body weight) produced a significant increase of cells in the G0 which is the indication of cell arrest or apoptosis. Reduction of cell viability by 2ME + CP treatments is due to apoptotic cell death. This combination therapy produced a significant inhibitory effect of cell proliferation and augmentation of cell accumulation in the G0 phase (i.e. apoptosis). Apoptosis is validated by Fluorescence staining of control and treated S-180 tumour cells with Acridine Orange and EtBr dye. Moreover, a steady increase in the frequency of complex chromosomal aberrations (i.e. tri-, qudri-radial translocations) in tumour cells was noted in that particular concentration of combination therapy treated series along with the increase in dead cell frequency and tumour regression pattern. It is assumed that, these chromosomal abnormalities or damages recorded in higher frequency prevent the affected metaphases to enter into the next cell cycle through apoptosis or necrosis. This study introduces a novel combination, where this particular concentration of 2ME + CP (i.e. 6.5 mg 2ME/kg body weight + 75 mg CP/kg body weight) not only enhanced the life span of tumour bearing mouse and decreased the tumour volume antagonistically but also inhibited the viable cell population synergistically, which could serve as a potential effective regimen for cancer treatment.